We are other members and don't have access to your husband's account or any past history he may have with Ebay.
If he previously had an account which was banned, or is associated in any way with an account which was banned, that could be why this account has been closed.
However, that is entirely speculation.
Unfortunately, as is often reported in this forum, Customer Services are not allowed to discuss with members why their account has been permanently suspended so he may never know the actual reason.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)